The Fresh Water Polyp Hydra (IMAGE) Kiel University Caption The fresh water polyp Hydra as a model system shows possible links between overfed microbes and the development of disease. Credit © Kiel Life Science Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.